The dawn of the jet-age
The first part of this series is here — I suggest you begin there
The final report of the Cohen Commission was delivered in February 1955, and the cause of the Comet accidents was clear. Accumulated stress on the passenger cabin had led to catastrophic failure of the fuselage. It was a terrible indictment of the design team, who had constructed the skin of the aircraft from aluminum alloy less than 1 mm thick — “as thin as a postcard” to quote the exact words of one engineer on the project, in order to save weight. Though the structure had been tested numerous times, no one had thought of the accumulation of stress due to ‘metal fatigue’.
But the Comet had also demonstrated that propeller-driven aircraft of the time, that had rattled and roared through the skies for so long, were now obsolete. The Boeing Company, which had effectively invented the modern monoplane with its Model 247 but lost the market to arch-rival Douglas Aircraft’s DC-3, saw an opportunity to leapfrog the competition and dominate the civil aircraft market.
The Seattle, Washington-based manufacturer had a talented design team. They had already built two swept-wing jet bombers for the US Air Force, the B-47 Stratojet and B-52 Stratofortress. (US military aircraft are designated with a type name prefix letter that denotes the airplane’s principal function; for example, bombers are prefixed ‘B-’, Pursuit aircraft ‘P-’, fighters ‘F-’, transports ‘C-’, etc.) The B-52 was an inspired creation that was famously designed over a weekend in a hotel room, first flew in 1952, and remains in active service today.
Boeing set out to design a civil jet transport that would incorporate the bitter lessons learned from the Comet, but, hopefully, prove far more capable than the British aircraft. Dubbed the Model 367, it was a closely guarded secret within the company.
The designers of the Comet had been rather hazy on the commercial applications of their aircraft. Restricted by the technology available and obsessed with the ‘Empire Routes’, they endowed the Comet with limited commercial flexibility. The Ghost turbojet engines that powered it, designed by Frank Halford and built by de Havilland, had a thrust rating limited to 4,450lb (20kN) each.
The Comet’s thin swept-back wings meant it was much faster than propeller aircraft, cruising at 400 knots (nautical miles per hour) despite the puny engines. But its range was limited to 1,300 nautical miles (roughly three hours’ flying time) because the thin wing restricted the size of the fuel tanks. The aircraft’s fuselage diameter was also relatively small at 8ft 6in (2.6m), to the detriment of baggage space, as an additional fuel tank had to fit in there too.
All this meant that the Comet had space for a maximum of only 44 passengers, and needed to stop frequently to refuel. Hence the absurd (to our modern eyes) six stops to reach Johannesburg or Colombo, each destination being approximately the same distance from London. On the route to Ceylon (Sri Lanka), the Comet would land in both Karachi and Bombay, despite a sector time between those cities of less than two hours. Clearly, route optimization was a concept that had not yet been invented.
Upgrades to the original
De Havilland’s engineers, no doubt urged on by BOAC, took all these considerations into account when redesigning the Comet after the disasters with the type’s first iteration, the Comet 1.
But even before the Comet 1 disasters occurred, work was proceeding on an upgraded model, the Comet 2, powered by Rolls-Royce Avon axial-flow turbojet engines. The Comet 2 prototype made its maiden flight in February 1952, and BOAC placed an order for 11, followed by Australia-based British Commonwealth Pacific Airlines (BCPA) for six more. But those orders were cancelled in the wake of the Comet 1 crashes.
Subsequently, modified Comet 2s, with oval windows in lieu of their original rectangular fittings, were delivered to Britain’s Royal Air Force with the military type designation Comet C.2. Operated mainly by Transport Command, the RAF’s C.2s served safely and reliably for many years, sometimes seen at Katunayake Airport, Colombo on transit between the UK and Australasia.
Even before the Comet 1’s structural failures, a longer-range intercontinental design, the Comet 3, was on the de Havilland drawing boards. Fitted with oval windows from the outset, and an extended fuselage that could comfortably accommodate 78 passengers, the Rolls-Royce Avon-powered prototype first flew in July 1954. In December 1955, spurred by a tentative order already placed by Pan American World Airways, it was taken on a round-the-world demonstration tour. But Pan Am cancelled its order, and no more Comet 3s were built.
The final model, named Comet 4, was larger, heavier and faster, with its much more powerful Rolls-Royce Avon 524 engines (10,500lb thrust each). So-called ‘pinion’ tanks on the wings (as fitted to the sole Comet 3) allowed extra fuel to be carried, as trans-Atlantic flights had become the most important market. By the time Comet 4 was flying in 1958, the Suez Canal was no longer under British control (Egypt nationalized it in 1956), and the Empire Routes for which the new jetliner was originally intended were increasingly irrelevant.
But the USA was not the only superpower. The Russian ‘bear’ had begun baring its claws in the recently metamorphosed USSR with world ambitions of its own. Soviet engineers had watched the Comet debacle with great interest. They rapidly repurposed an existing bomber, the Tupolev Tu-16 ‘Badger’, with a wider fuselage, and created the Tu-104 airliner in 1955 (‘Badger’ was an example of the NATO-designated ‘reporting’ or code names for all Soviet military aircraft types.) A year later it was operating passenger services, thereby becoming the second jetliner to do so.
Western governments were unaware of theTu-104’s development, so its unexpected introduction on the Moscow-to-London route in March 1956 was sensational — a ‘Sputnik moment’, which showcased Soviet capabilities. For two years the Tu-104 was the world’s only passenger jet in service, flying from Moscow to London, Budapest, Prague, Brussels, Beijing, Ottawa and Delhi.
But the Tu-104 (and its shorter-range derivative the Tu-124) was essentially a military jet; the civil versions of both even retained the distinctive ‘glasshouse’ nose that housed the navigator. With rakishly swept-back wings, the Tu-104 was a handful to fly, especially at the lower speeds required at busy civil airports. High approach speeds and limited braking performance meant that drag chutes were often deployed to stop within available runway lengths. Engine start would send sheets of flame shooting out the rear of the Mikulin AM-3 turbojets, terrifying ground staff. A poor safety record also ensured that the Tu-104 would never be successful, even by the more lax standards of the Soviets.
Boeing unveiled its prototype Model 367–80 in August 1955, with the company’s chief test pilot, the legendary Alvin M. ‘Tex’ Johnson, putting the ‘Dash 80’ through a spectacular — and unauthorized — ‘barrel-roll’ during its maiden flight. A correctly performed barrel roll maintains 1G throughout the maneuver, placing no untoward stress on the airframe, so it was not an unsafe thing to do. But it did attract a lot of attention, and remains a talking point to this day. Understandably, however, Boeing’s President Bill Allen was appalled, and the dramatic exercise was never repeated in Boeing test flights.
Boeing engaged the airlines from the start, and discussions ensured that the prototype, now named the Model 707, had a wider fuselage extended from 11ft (3.35m) to 12ft 4in (3.75m) in order to allow six-abreast seating. This was a lesson well learned, as it was American Airlines’ insistence on making the DC-3 wide enough to have three seats across which led to the Boeing Model 247 being eclipsed.
This measurement has since become the de facto standard for all ‘single-aisle’ jets, with even the Airbus A320’s fuselage (at 13ft or 3.95m) being only marginally wider.
By suspending the 707’s four Pratt & Whitney JT3D engines in pods beneath the wings (the Comet and Tupolev’s Tu-104 and Tu-124 had them tucked in near the wing roots), Boeing was compelled to have a taller landing gear. This and the wider fuselage meant that the passenger cabin could be continuous, with the area below it used as baggage holds. The classic ‘tube-shaped’ jet aircraft template was now set in stone.
When the first production Boeing 707 flew in December 1957 it was bigger, faster (by almost 100 mph), and could range farther than the Comet. With a large order from Pan Am to spur it into production, and Douglas scrambling to design the competing DC-8, the balance had tipped in favour of the Americans.
The Comet 4
Finally, the redesigned Comet 4, with its distinctive oval-shaped windows, was certified and entered service with BOAC in September 1958. Within a month the British flag-carrier had inaugurated the world’s first trans-Atlantic jet service between London and New York. The strong winter jetstream (west to east) winds meant, however, that the Comets often had to make a refueling stop in Gander, Newfoundland on the westbound crossing.
Within weeks, Pan American inaugurated a rival trans-Atlantic service utilizing its new flagship 707, which was faster than the Comet but still occasionally required this stop. Pan Am’s speed advantage and rival El Al’s cheeky advertising campaign boasting “No Goose, No Gander” on their Bristol Britannia turboprop service in the same route, stole the Comet’s thunder. This eventually induced BOAC to also place a substantial order for the 707 (powered by Rolls-Royce Conway turbofan engines).
The Comet 4 eventually enjoyed a reasonably successful career, with 74 examples built including all variations of the type, before production ceased in 1964. One variant with a longer fuselage and no pinion fuel tanks, intended for regional routes was, the Comet 4B. Of the 18 examples built, 14 were sold to British European Airways, with the remainder going to Olympic Airways of Greece.
The Comet 4C was the final version; combining a fuselage 6ft longer than that of the original Comet 4 with the latter’s wing, it was the most successful variant.
BOAC’s order for 19 Comet 4s aside, other customers for the ‘basic’ type were Aerolíneas Argentinas and East African Airways; the 4C was sold to Misrair (later renamed United Arab Airlines), Middle East Airlines (Beirut),Mexicana, Sudan Airways and Kuwait Airways. A sole Comet 4C was bought by Saudi Arabian Airlines as a VIP aircraft for the Saudi Royal Flight.
Several other airlines including Air Ceylon, Air-India, Qantas, Malaysian Airways and Cyprus Airways operated the type at various times, either on wet-lease from their current owners or as ‘hand-me-downs’, as in the case of the five ex-BOAC Comet 4s bought by Malaysian Airways (later named Malaysia-Singapore Airlines; MSA), and another from the BOAC fleet sold to Aerovias Ecuatorianas (AREA-Ecuador). Finally, Dan-Air, a British charter carrier, acquired many pre-owned Comet 4s of all three sub-types (comprising 14 Comet 4s, fourteen 4Bs and ten 4Cs), and flew them until the last survivor was retired from service in November 1980.
The basic Comet airframe design, with its fatal flaws finally fixed, proved successful and durable in both civil and military applications. Apart from the C.2s and, later, C.4s (militarised Comet 4s) of the RAF, two examples of the original type, Comet 1A, served the Royal Canadian Air Force (RCAF) Transport Command with distinction for more than a decade. But only after they had been returned to de Havilland for structural modifications in the aftermath of the commercial Comet 1 accidents.
The last two production Comets 4Cs never entered airline service but were modified to meet a RAF requirement for a maritime patrol and anti-submarine warfare (ASW) platform. Built by Hawker Siddeley (which had absorbed de Havilland and other UK manufacturers) and powered by Rolls-Royce Spey turbofan engines, this design evolved into the Nimrod. It incorporated major changes and additions to the basic Comet fuselage, including an internal weapons bay, an extended nose for radar, and other housings for electronic warfare devices.
Entering service in 1969, the Nimrod was flown by five RAF squadrons, and saw service during the Falklands War, the Gulf War, and in Afghanistan and Iraq. Other planned variants, however, including an AWACS (Airborne Warning and Control System) platform, failed to materialise.
The last operational Comet, a 4C built in 1963, was used by Britain’s Aeroplane and Armament Experimental Establishment (A&AEE) at Boscombe Down as a flying research laboratory named ‘Canopus’ until its retirement in 1997.
In 2011, when the last RAF Nimrod was grounded, the curtain was finally rung down on the heritage of Geoffrey de Havilland’s Comet design, which had revolutionized the aviation world since the prototype’s first flight some 62 years before.
This is part of a series on the propliners of the 1950s and the slow transition to the jet age. It all began with the DC-3 of course, and my columns move through the other Douglas propliners, the Boeing 377, Lockheed’s Electras and the elegant Constellation. The Brabazon Committee which sparked such a wave of innovation in the UK with the Vickers Viscount, the Bristol Britannia and the ill-fated de Havilland Comet. Many other significant aircraft, such as Avro Canada’s innovative but aborted C-102 passenger jet and the Sud-Aviation Caravelle, which led us into the start of the Jet Age have columns too.
A few quirky segues I couldn’t resist: the ‘Double Sunrise’ flights between my two homelands Ceylon and Australia; the wonderful Carvairs and that very British habit of taking your car on holiday. I also had to write a paean to my beloved A380 and all my pilot friends in the Gulf as COVID ended that little dream.
Thanks for reading and I hope you enjoyed the series as much as I have relished writing them. My special thanks to my old friend, mentor, editor and repository of knowledge Roger Thiedeman, for all the encouragement and support throughout this project.